Magnetic Flux Calculator
Find the magnetic flux through a flat surface given the field strength, area, and the angle between the field and the surface normal.
T
m²
°
Φ = B · A · cos θ
- 1
Angle in radians
30° × π ÷ 180 = 0.523599 - 2
cos θ
cos(30°) = 0.866025 - 3
B × A
0.5 × 0.2 = 0.1 - 4
Magnetic flux Φ
B·A × cos θ = 0.1 × 0.866025 = 0.086603Flux is zero when the field is parallel to the surface (θ = 90°) and maximum when perpendicular (θ = 0°).
How does this calculator work?
Magnetic flux equals the field strength B times the area A times the cosine of the angle θ between the field and the surface normal: Φ = B·A·cos θ. Enter B in tesla, A in square metres, and θ in degrees to get the flux in webers, which peaks at B·A when θ is zero.
Formula
How this is calculated
Magnetic flux Φ measures how much magnetic field passes through a surface. It is the product of the magnetic flux density B (in tesla), the surface area A (in square metres), and the cosine of the angle θ between the field vector and the surface normal. The result is given in webers (Wb), where 1 Wb = 1 T·m².
The angle θ is entered in degrees and converted to radians internally before taking its cosine. When θ = 0° the field is perpendicular to the surface (parallel to the normal) and the flux is at its maximum value B·A. When θ = 90° the field lies in the plane of the surface and no field lines cross it, so the flux is zero. Angles above 90° give a negative cosine, meaning the flux passes through the surface in the opposite sense.
This model assumes a uniform field and a flat surface, so B is constant across the area. For a coil of N turns the total linked flux is N·Φ. Negative or fractional inputs are accepted; non-numeric entries return no result.
Frequently asked questions
θ is the angle between the magnetic field vector and the normal (perpendicular) to the surface, not the surface itself. At θ = 0° the field is perpendicular to the surface and flux is maximal.
The weber (Wb), equal to one tesla times one square metre (T·m²). One weber is also one volt-second.
Multiply the single-loop flux Φ by the number of turns N to get the total flux linkage NΦ used in Faraday's law.
Also known as
TG we-Calculate Editorial Team. (2026). Magnetic Flux Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/magnetic-flux-calculator
TG we-Calculate Editorial Team. "Magnetic Flux Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/magnetic-flux-calculator.
TG we-Calculate Editorial Team, "Magnetic Flux Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/magnetic-flux-calculator
@misc{wecalculate_magnetic_flux_calculator, title = {Magnetic Flux Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/magnetic-flux-calculator}}, year = {2026}, note = {TG we-Calculate} }
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